Path: utzoo!attcan!uunet!samsung!munnari.oz.au!basser!ultima!hades!ing
From: ing@hades.OZ (Ian Gold)
Newsgroups: comp.lang.c++
Subject: Define's and Devices.
Keywords: defines, devices
Message-ID: <478@hades.OZ>
Date: 25 Nov 89 00:39:45 GMT
Organization: Ausonics Pty Ltd, Sydney, Australia
Lines: 85


	I would like to write object orientated code in C++ but am having 
trouble coping with two concepts. Perhaps my C background is plaguing me.  
Perhaps I am a hypocondriac.

	The first problem is the "#define syndrome".  Assume I have a keyboard
defined as

	enum keys { ENTER = 0x13,
		    ESC   = 0x27,
		    A_CHR = 0x41,
		    B_CHR = 0x42,
			.
			.
			.
		  };

In C I would declare this globally so everybody knows about it.  What I
would like to do in C++ is something like

	class keys
	{
	public:
		enum keys { ENTER = 0x13 
				.
				.
				.
			  };
	};

	class program : keys
	{
	public:
		void program :: function(void) { return keys::ENTER; }
	}

and allow it to be inherited only by the classes that need it.  I realise
that this is much slower than using #defines and would only be useful if
one uses multiple inheritance.  The problem is that the above example is
NOT C++.  DOES ANYBODY KNOW HOW OR IF I CAN ACHIEVE THE ABOVE IDEAS EFFICIENTY
IN C++ !  Is the following code the best way out.

	class keys
	{
	public:
		int ENTER() { return 0x13; } 
			.
			.
			.
	};

	class program : keys
	{
	public:
		void program :: function(void) { return keys::ENTER(); }
	}


	My second problem is that of devices.  Say I have three CPU's
2 keyboards and half a VDU.  Somewhere I must declare these as being the
only devices avaliable.  IS THE FOLLOWING CODE THE "CORRECT" WAY TO HANDLE
THE SITUATION.

	class program
	{
		CPU 		cpu1;
		CPU 		cpu2;
		CPU		cpu3;
		KEYBOARD	keyboard1;
		KEYBOARD	keyboard2;
		VCU		vdu(0.5);	
		boolean		program();
	public:
		go() { keyboard1.reset(); 
		       keyboard2.reset(); 
		       vdu.reset();
		       program();         }
	};

	void main(void)
	{
		program a;

		a.go();
	}